Not all filmmakers pull it off, but it's something the Dardennes, Jean-Pierre and Luc, are remarkably good at — making us understand just what we share with their characters, working-class people in industrial Belgian cities who are decidedly neither heroes nor villains, just ordinary folk trying to get by. [...] their effort is even more remarkable here, because the writer-directors are working for the first time with a bona fide, glamorous movie star: The fact that it works so well is a tribute both to Cotillard's committed, selfless work and to the Dardennes' unerringly authentic instincts. Cotillard plays Sandra, a mother of two young children who works at a solar panel factory. With the help of a concerned and supportive husband (Fabrizio Rongione), Sandra heads out to knock on doors. Sandra is a mass of jangled nerves, prone to popping Xanax to get through the day, or escaping to bed in the afternoon. With no makeup, a messy ponytail and a uniform of jeans and tank tops revealing colorful bra straps, Cotillard is stripped of glamour. Two Days, One Night," an IFC Films release, is rated PG-13 by the Motion Picture Association of America "for some mature thematic elements.